CATH Documentation

Beta bulges are regions of irregularity in a beta sheet, where the
normal pattern of hydrogen bonding is disrupted, e.g. by the insertion of
an extra residue. A bulge usually involves two or more residues in
the bulged strand, opposite a single residue in the adjacent strand.
These irregularities have been identified and classified
automatically. In all, five types of beta-bulge were identified:
classic, G1, wide, bent and special. Bulges were found to occur
frequently in proteins, on average more than two bulges per protein.
In general, beta-bulges produce two main
changes in the structure of a beta sheet: (i)disruption of the normal alternation
of side-chain direction (ii) accentuation of the twist of the sheet, altering
the direction of the surrounding strands.